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Inventory no. 52029 - Epact entry

Epact number: 84214

Astronomical Compendium

Signed by Ulrich Schniep
1550-70; Munich
Gilt brass; 53 mm in diameter

Main text

This compendium includes a nocturnal, a lunar volvelle, a universal equinoctial sundial, a compass, and a table of latitudes.

It is very similar in conception and features to at least one other circular compendium by Ulrich Schniep (Epact 84682). Though it also has inscriptions in Latin and Italian (the latter only for the names of the winds), the presence of Dutch for the directions of the compass might suggest that it was made for a Dutch client.

Source museum: Museum of the History of Science, Oxford
Museum number: Inventory no. 52,029

Detailed text

This circular compendium has a main drum and a cover, with a suspension ring. The diameter is 53 mm and the depth 12 mm. Around the outside of the drum is the signature 'HOC OPVS HOROLOGIVM GENERALE FECIT VLRICVS SCHNIEP DE MONACO'.

The top cover carries a nocturnal whose volvelle also gives the length of day and night throughout the year. The nocturnal has a calendar scale with the months named in Latin. Each month is divided to 10 and 2, and numbered by 10 (adjusted for the length of the month). The date against the hinge is approximately 25 April.

The hour scale of the volvelle runs 3 to 12 to 9, each hour has a small projecting tooth and is divided to |1/2| and |1/4|. The pointer is marked 'A' and is placed in the middle of the cut away section of daylight hours which reveals the calendar scale. The volvelle carries a general inscription 'NOCTVRNALE CVIVS OPE PER EXTREMAS VRSAE MINORIS STELAS NOCTVRNO TEMPORE'. The rotating, jointed rule above the volvelle is marked 'INDEX HORA NOCTI'.

The volvelle also has two apertures through which the length of day and night throughout the year is revealed. The latitudes 38, 41, 44, 47, 50° ('ELEVATI: POLI ART:') are catered for and by the pointer there is the inscription 'INDEX .A. AD DIEM MENSIS MOVEATVR COLOCETVR', which continues either 'QVANTI: DIEI' or 'QVANTI: NOCTI'. Each of the five hour scales is divided to |1/2|, and values in minutes are given for the maximum and minimum lengths of the day (except for latitude 41° which is given as exactly 15 and 9 hours, respectively). However, the maximum values in minutes for the other four latitudes have mistakenly been used for the minimum values as well.

The reverse of the cover has a lunar volvelle. There is an outer scale of hours 1 to 12, 1 to 12, each divided to |1/4|, and the volvelle is cut away around a pointer to reveal a scale for the age of the moon 0 to 29[|1/2|]. The volvelle is captioned 'INDEX DIERVM AETATIS LVNAE' and its scale of hours runs 3 to 12 to 9, with each hour again divided to |1/4|. There is a circular aperture to reveal a diagram of the phases of the moon and an aspectarium with the symbols for conjunction, trine, quadrature and sextile.

Folding into the drum of the main box is a universal equinoctial sundial. Its gnomon can be rotated to point either up or down; in either case it is sprung to ensure that it is perpendicular to the hour ring. The hour ring runs I to XII, I to XII for common hours and is surrounded by a sliding ring marked 1 to 24 for Italian hours. Both scales have their hours divided to |1/4|. The underside of the hour ring is marked 'CIRCVLVS AEQVINOCTALIS ET MONSTERAT HORAS GERMANI: ET ITAL:'.

Rather than a folding arc set against the outer edge of the hour ring (as in Epact 84682), the latitude scale is engraved on a short brass arm
set on the inside of the hour ring. The hinged, swivelling piece fits in a notch at the midday point and is marked on one side 'ELEVATION: POLI'. The other side carries a double latitude scale of degrees 0 to 64 and 8 to 72, each portion divided to 16 and 4 and numbered by 16. At either end of the scale is 'IZ' (i.e. 12), and the arm has a small circular hole at its end.

The latitude scale is attached to the plate of the main drum carrying the compass and a wind- and compass-rose. The compass bowl is 21 mm in diameter and its silvered base plate has a single arrow line for orientation. The needle is missing. Around the compass is a semicircular scale of degrees 0 to 90, 0 to 90, divided to 10 and 2, and numbered by 10. The other semicircle of the engraved band is marked 'DECLINACIO: MANGNETIS'.

The surrounding band carries a wind rose with the eight classical names in Italian. The outer ring carries the names of the eight principal directions in Dutch, and between the wind and compass roses are 16 pointers, of which those for the four cardinal directions carry abbreviations of their Latin names.

The base of the instrument has a table of the latitudes. The circular table is inscribed 'POLI ART. LATITV:' and gives the latitudes of 32 places in approximately alphabetical order.

Stephen Johnston

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